On 19 December 2017 at 18:52, Keno Fischer <keno@xxxxxxxxxxxxxxxxxx> wrote: > Yes it seems like an EINTR return should be considered a bug, so please drop > this from your patch queue. Thanks for the follow up. Okay -- thanks for the info. Cheers, Michael > On Dec 19, 2017 14:57, "Michael Kerrisk (man-pages)" > <mtk.manpages@xxxxxxxxx> wrote: >> >> >> Hi Keno, >> >> On 12/04/2017 10:03 PM, Keno Fischer wrote: >> > Hi Michael, >> > >> > I was hoping to get a clear statement one way or another from the kernel >> > maintainers as to whether an EINTR from stat() is supposed to be allowed >> > kernel behavior (hence the RFC in the subject). If it's not, then I >> > don't think >> > it should be documented, even if there is buggy filesystems that do at >> > the moment. >> > So I'd say let's hold off on applying this until more people have had a >> > chance >> > to comment. If it would be more convenient for you, feel free to drop >> > this from your >> > patch queue and if appropriate, I'll resend a non-RFC version of this >> > patch for you >> > to apply, once a conclusion has been reached. >> >> So, was there any further conclusion on this? >> >> Cheers, >> >> Michael >> >> > On Mon, Dec 4, 2017 at 3:58 PM, Michael Kerrisk (man-pages) >> > <mtk.manpages@xxxxxxxxx> wrote: >> >> Hello Keno >> >> >> >> On 12/03/2017 04:15 AM, Keno Fischer wrote: >> >>> Resending as plain text (apologies for those receiving it twice, and >> >>> those that got >> >>> an HTML copy, I'm used to my mail client switching that over >> >>> automatically, which >> >>> for some reason didn't happen here). >> >>> >> >>> >> >>> This is exactly the discussion I want to generate, so thank you. >> >>> I should point out that I'm not advocating for anything other >> >>> than clarity of what kernel behavior user space may assume. >> >> >> >> So, should the documentation patch be applied at this point, or >> >> dropped? >> >> >> >> Thanks, >> >> >> >> Michael >> >> >> >> >> >>> On Sat, Dec 2, 2017 at 9:25 PM, Matthew Wilcox <willy@xxxxxxxxxxxxx> >> >>> wrote: >> >>>> On Sat, Dec 02, 2017 at 07:23:59PM -0500, Keno Fischer wrote: >> >>>>> The catalyst for this patch was me experiencing EINTR errors when >> >>>>> using the 9p file system. In linux commit 9523feac, the 9p file >> >>>>> system was changed to use wait_event_killable instead of >> >>>>> wait_event_interruptible, which does indeed address my problem, >> >>>>> but also makes me a bit unhappy, because uninterruptable waits >> >>>>> prevents things like ^C'ing the execution and some debugging >> >>>>> tools which depend on being able to cancel long-running operations >> >>>>> by sending signals. >> >>>> >> >>>> Wait, wait, wait. killable is not uninterruptible. It's "can accept >> >>>> a signal if the signal is fatal". ie userspace will never see it. >> >>>> So, no, it doesn't prevent ^C. It does prevent the debugging tool >> >>>> you're >> >>>> talking about from working, because it's handling the signal, so it's >> >>>> not >> >>>> fatal. >> >>> >> >>> This probably shows that I've been in REPL based environments too >> >>> long, >> >>> that catch SIGINT ;). You are of course correct that a fatal SIGINT >> >>> would >> >>> still be delivered. >> >>> >> >>>>> I realize I'm probably 20 years too late here, but it feels like >> >>>>> clarificaion on what to expect from the kernel would still go a long >> >>>>> way here. >> >>>> >> >>>> A change to user-visible behaviour has to be opt-in. >> >>> >> >>> I agree. However, it was my impression that stat() can return EINTR >> >>> depending on the file system. Prior to the referenced commit, >> >>> this was certainly true on 9p and I suspect it's not the only network >> >>> file >> >>> system for which this is true (though prior to my experiencing this >> >>> with 9p, the only >> >>> time I've ever experienced it was on HPC clusters with who knows what >> >>> code providing the network filesystem). If it is indeed the case that >> >>> an EINTR return from stat() and similar is illegal and should be >> >>> considered >> >>> a kernel bug, a statement to that extent all I'm looking for here. >> >>> >> >> >> >> >> >> -- >> >> Michael Kerrisk >> >> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ >> >> Linux/UNIX System Programming Training: http://man7.org/training/ >> > >> >> >> -- >> Michael Kerrisk >> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ >> Linux/UNIX System Programming Training: http://man7.org/training/ -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
